1. Technical Field
The present invention relates to a truck/trailer assembly which is intended to operate at a high load capacity for travel over a route where there are load limitations, such as on a public highway, and also adapted to maneuver the trailer at a site, such as a loading or unloading site.
2. Background Art
When a truck and a trailer are traveling over a highway, the load limitations for the truck and the trailer depend not only on the number of axles for the ground engaging wheels which support the truck and the trailer, but also the spacing of these wheels. For this reason, it is not uncommon for a trailer to be provided with a relatively long reach or tongue by which the trailer is attached to the truck. This spaces the wheels of the trailer a sufficiently large distance from the wheels of the truck so that the total load capacity of the truck and trailer combination can be increased substantially.
As a general rule, for a truck and trailer combination, the addition of another axle to the truck or trailer generally increases the load capacity by about 1500 to 2000 pounds per axle. Also, if the trailer can be spaced rearwardly of the truck a further distance, there is an increase in load limit that is equivalent to about 1500 to 2000 pounds for each foot that the trailer can be spaced further rearwardly from the truck or tractor.
In one general arrangement, the trailer has a forward and a rear set of wheels, with the rear wheels being mounted to the base frame of the trailer and the forward wheels being mounted to the reach. Thus, the front wheels are steerable, in that when the truck is executing a turn, thus causing the reach to swing laterally to an angle relative to the trailer, the front wheels of the trailer turn with the reach so as to cause the trailer to properly follow the truck as it is executing a turn. While this arrangement makes it possible for the trailer to be positioned at a more rearward location relative to the truck for rather effective over the road travel, it also makes it extremely difficult to manipulate the trailer in any backup maneuver for more than a very short distance. For example, if the trailer is to function as a dump trailer which must be backed up to a particular location to discharge its load, it would generally be necessary to use a semi-trailer which has only one set of wheels on one axle or on two closely spaced axles, with the forward end of the trailer being supported by the truck. Accordingly, the trailer having the rather elongate reach with the steerable set of front wheels is generally used under circumstances where the load can be discharged in a manner that does not require backing up of the trailer.
In view or the foregoing, it is an object of the present invention to provide a novel trailer and also a truck and trailer assembly which is able to travel effectively in a traveling mode where the trailer is spaced further rearwardly ot the truck, with the trailer having a front set of steerable wheels and a rear set of wheels engaging the road surface, and also to be able to operate in a backup mode where the trailer is positioned more closely to the truck with only the rear set of wheels engaging the ground.
It is a further object of the present invention to provide effective arrangements for the mechanism to move the forward trailer steering wneels from the ground and secure the reach to the trailer for the maneuvering mode of operation.
Other objects of the present invention will become apparent from the following disclosure of the invention and the description of the preferred embodiments.